This application is based on an application No. 2007-36735 filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a communication control device for controlling communications between a main body control unit and each paper feeding control unit, wherein the main body control unit for controlling an image forming unit is connected, via communication lines, to a plurality of the paper feeding control units which control supply of recording papers to the image forming unit, respectively, by corresponding to a plurality of paper feeding cassettes. Further, the present invention relates to an image forming device in which the image forming unit and the paper feeding control unit are connected via the communication control device.
2. Description of the Related Art
An image forming device such as a digital copying machine is constituted to be able to have a plurality of option units such as a sorter and a plurality of paper feeding cassettes detachably attached to a main body of the device.
Japanese Unexamined Patent Application Publication No. 2000-351252 discloses a structure which, when mounting a plurality of option units to a printer main body, shares serial communication lines that connect a control unit of the printer main body and control units of each of the option units by cascaded connecting the serial communication lines in a cascade manner between each of the option units.
Each of the option units includes communication means that includes a first connector for transmitting and receiving signals by being connected to the printer as well as a second connector for transmitting and receiving signals to/from another option unit. The communication device is constituted to transmit a signal that is received from the printer via the first connector to another option unit via the second connector, and to transmit a signal that is received from another option unit via the second connector to the printer via the first connector.
Further, the communication means includes a return path for enabling transmission of signals to the printer via the first connector without transmitting the signals to another option unit via the second connector.
With the above-described structure, combinations and connecting orders of the option units that are connected to the serial communication lines can be set freely.
In order to achieve the same object, it is also possible to have a communication control device that employs a polling system for communicating with each paper feeding cassette by switching address data on address lines, through connecting a device main body and a plurality of paper feeding cassettes as the option units via common serial communication lines and a plurality of the address lines for selecting each paper feeding cassette.
For example, when the plurality of paper feeding cassettes are piled up in a vertical direction at a bottom part of the device main body, the serial communication lines and the address lines are connected detachably via drawer connectors that are provided to the device main body and each of the paper feeding cassettes, and communications are performed by executing polling in order from a paper feeding cassette to which the communication control device is mounted first, i.e. a paper feeding cassette that is connected on the highest drawer, towards the lower drawers one by one.
The paper feeding control unit provided to each of the paper feeding cassettes drive- or stop-controls a paper feeding roller based on a control instruction that is received via the communication control device from the main body control unit via the serial communication line, and drive- or stop-controls a transporting roller for transporting the fed recording paper to a main body side.
The transporting rollers controlled by each of the paper feeding control units are provided along a common transporting path to the main body side. Thus, the paper feeding control units on an upper drawer side (on the downstream side along the transporting path) need to drive- or stop-control the corresponding transporting rollers for transporting the recording paper that is fed by the paper feeding control unit on a lower side (on the upstream side along the transporting path) towards the main body.
However, with the above-described communication control device that employs the polling system, a necessary control instruction is transmitted to each of the paper feeding control units in order at a prescribed interval. Therefore, even when it is required to stop or drive the transporting rollers of each paper feeding cassette at once, for example, there is delay of several milliseconds in the time at which a control instruction reaches the paper feeding control units of each paper feeding cassette. As a result, synchronicity of the control cannot be secured. In the above-described case, the paper feeding control unit mounted to the paper feeding cassette of the highest drawer is to receive the control instruction at the earliest time, and the paper feeding control unit mounted to the paper feeding cassette of the lowest drawer is to receive the control instruction at the latest time.
The paper feeding control unit of a lower drawer that receives a control instruction for stopping the transporting roller later than that of a upper drawer exhibits delay in the timing for stopping the transporting roller for an amount of delay time in receiving an instruction with respect to that of the transporting roller of the upper drawer. Therefore, the recording paper becomes bent between the transporting rollers located on the upper drawer and on the lower drawer.
Similarly, the paper feeding control unit in the lower drawer that receives the control instruction for driving the transporting roller later than that of the upper drawer exhibits delay in the timing for driving the transporting roller for an amount of delay time in receiving the instruction with respect to that of the transporting roller of the upper drawer. Therefore, there is a tension supplied to the recording paper between the transporting rollers located on the upper drawer and on the lower drawer.
This results in causing such problems that the recording paper may be fed obliquely to the transporting path, the recording paper may be jammed, or the recording paper may be damaged.